Sinatra is a DSL for quickly creating web applications in Ruby with minimal effort:

``` ruby # myapp.rb require ‘sinatra’

get ‘/’ do ‘Hello world!’ end ```

Install the gem:

shell gem install sinatra

And run with:

shell ruby myapp.rb

View at: http://localhost:4567

It is recommended to also run gem install thin, which Sinatra will pick up if available.

Table of Contents


In Sinatra, a route is an HTTP method paired with a URL-matching pattern. Each route is associated with a block:

``` ruby get ‘/’ do .. show something .. end

post ‘/’ do .. create something .. end

put ‘/’ do .. replace something .. end

patch ‘/’ do .. modify something .. end

delete ‘/’ do .. annihilate something .. end

options ‘/’ do .. appease something .. end

link ‘/’ do .. affiliate something .. end

unlink ‘/’ do .. separate something .. end ```

Routes are matched in the order they are defined. The first route that matches the request is invoked.

Route patterns may include named parameters, accessible via the params hash:

ruby get '/hello/:name' do # matches "GET /hello/foo" and "GET /hello/bar" # params[:name] is 'foo' or 'bar' "Hello #{params[:name]}!" end

You can also access named parameters via block parameters:

ruby get '/hello/:name' do |n| # matches "GET /hello/foo" and "GET /hello/bar" # params[:name] is 'foo' or 'bar' # n stores params[:name] "Hello #{n}!" end

Route patterns may also include splat (or wildcard) parameters, accessible via the params[:splat] array:

``` ruby get ‘/say//to/’ do # matches /say/hello/to/world params[:splat] # => [“hello”, “world”] end

get ‘/download/.’ do # matches /download/path/to/file.xml params[:splat] # => [“path/to/file”, “xml”] end ```

Or with block parameters:

ruby get '/download/*.*' do |path, ext| [path, ext] # => ["path/to/file", "xml"] end

Route matching with Regular Expressions:

ruby get %r{/hello/([\w]+)} do "Hello, #{params[:captures].first}!" end

Or with a block parameter:

ruby get %r{/hello/([\w]+)} do |c| "Hello, #{c}!" end

Route patterns may have optional parameters:

ruby get '/posts.?:format?' do # matches "GET /posts" and any extension "GET /posts.json", "GET /posts.xml" etc. end

Routes may also utilize query parameters:

ruby get '/posts' do # matches "GET /posts?title=foo&author=bar" title = params[:title] author = params[:author] # uses title and author variables; query is optional to the /posts route end

By the way, unless you disable the path traversal attack protection (see below), the request path might be modified before matching against your routes.


Routes may include a variety of matching conditions, such as the user agent:

``` ruby get ‘/foo’, :agent => /Songbird (\d.\d)[\d\/]*?/ do “You’re using Songbird version #params[:agent][0]” end

get ‘/foo’ do # Matches non-songbird browsers end ```

Other available conditions are host_name and provides:

``` ruby get ‘/’, :host_name => /^admin./ do “Admin Area, Access denied!” end

get ‘/’, :provides => ‘html’ do haml :index end

get ‘/’, :provides => [‘rss’, ‘atom’, ‘xml’] do builder :feed end ```

You can easily define your own conditions:

``` ruby set(:probability) { |value| condition { rand <= value } }

get ‘/win_a_car’, :probability => 0.1 do “You won!” end

get ‘/win_a_car’ do “Sorry, you lost.” end ```

For a condition that takes multiple values use a splat:

``` ruby set(:auth) do |*roles| # <- notice the splat here condition do unless logged_in? && roles.any? {|role| current_user.in_role? role } redirect “/login/”, 303 end end end

get “/my/account/”, :auth => [:user, :admin] do “Your Account Details” end

get “/only/admin/”, :auth => :admin do “Only admins are allowed here!” end ```

Return Values

The return value of a route block determines at least the response body passed on to the HTTP client, or at least the next middleware in the Rack stack. Most commonly, this is a string, as in the above examples. But other values are also accepted.

You can return any object that would either be a valid Rack response, Rack body object or HTTP status code:

That way we can, for instance, easily implement a streaming example:

``` ruby class Stream def each 100.times { |i| yield “#i\n” } end end

get(‘/’) { } ```

You can also use the stream helper method (described below) to reduce boiler plate and embed the streaming logic in the route.

Custom Route Matchers

As shown above, Sinatra ships with built-in support for using String patterns and regular expressions as route matches. However, it does not stop there. You can easily define your own matchers:

``` ruby class AllButPattern Match =

def initialize(except) @except = except @captures =[]) end

def match(str) @captures unless @except === str end end

def all_but(pattern) end

get all_but(“/index”) do # … end ```

Note that the above example might be over-engineered, as it can also be expressed as:

ruby get // do pass if request.path_info == "/index" # ... end

Or, using negative look ahead:

ruby get %r{^(?!/index$)} do # ... end

Static Files

Static files are served from the ./public directory. You can specify a different location by setting the :public_folder option:

ruby set :public_folder, File.dirname(__FILE__) + '/static'

Note that the public directory name is not included in the URL. A file ./public/css/style.css is made available as

Use the :static_cache_control setting (see below) to add Cache-Control header info.

Views / Templates

Each template language is exposed via its own rendering method. These methods simply return a string:

ruby get '/' do erb :index end

This renders views/index.erb.

Instead of a template name, you can also just pass in the template content directly:

ruby get '/' do code = "<%= %>" erb code end

Templates take a second argument, the options hash:

ruby get '/' do erb :index, :layout => :post end

This will render views/index.erb embedded in the views/post.erb (default is views/layout.erb, if it exists).

Any options not understood by Sinatra will be passed on to the template engine:

ruby get '/' do haml :index, :format => :html5 end

You can also set options per template language in general:

``` ruby set :haml, :format => :html5

get ‘/’ do haml :index end ```

Options passed to the render method override options set via set.

Available Options:

List of locals passed to the document. Handy with partials. Example: erb "<%= foo %>", :locals => {:foo => "bar"}
String encoding to use if uncertain. Defaults to settings.default_encoding.
Views folder to load templates from. Defaults to settings.views.
Whether to use a layout (true or false). If it's a Symbol, specifies what template to use. Example: erb :index, :layout => !request.xhr?
Content-Type the template produces. Default depends on template language.
Scope to render template under. Defaults to the application instance. If you change this, instance variables and helper methods will not be available.
Template engine to use for rendering the layout. Useful for languages that do not support layouts otherwise. Defaults to the engine used for the template. Example: set :rdoc, :layout_engine => :erb
Special options only used for rendering the layout. Example: set :rdoc, :layout_options => { :views => 'views/layouts' }

Templates are assumed to be located directly under the ./views directory. To use a different views directory:

ruby set :views, settings.root + '/templates'

One important thing to remember is that you always have to reference templates with symbols, even if they’re in a subdirectory (in this case, use: :'subdir/template' or 'subdir/template'.to_sym). You must use a symbol because otherwise rendering methods will render any strings passed to them directly.

Literal Templates

ruby get '/' do haml '%div.title Hello World' end

Renders the template string.

Available Template Languages

Some languages have multiple implementations. To specify what implementation to use (and to be thread-safe), you should simply require it first:

ruby require 'rdiscount' # or require 'bluecloth' get('/') { markdown :index }

Haml Templates

Dependency haml
File Extension .haml
Example haml :index, :format => :html5

Erb Templates

Dependency erubis or erb (included in Ruby)
File Extensions .erb, .rhtml or .erubis (Erubis only)
Example erb :index

Builder Templates

Dependency builder
File Extension .builder
Example builder { |xml| xml.em "hi" }

It also takes a block for inline templates (see example).

Nokogiri Templates

Dependency nokogiri
File Extension .nokogiri
Example nokogiri { |xml| xml.em "hi" }

It also takes a block for inline templates (see example).

Sass Templates

Dependency sass
File Extension .sass
Example sass :stylesheet, :style => :expanded

SCSS Templates

Dependency sass
File Extension .scss
Example scss :stylesheet, :style => :expanded

Less Templates

Dependency less
File Extension .less
Example less :stylesheet

Liquid Templates

Dependency liquid
File Extension .liquid
Example liquid :index, :locals => { :key => 'value' }

Since you cannot call Ruby methods (except for yield) from a Liquid template, you almost always want to pass locals to it.

Markdown Templates

Dependency Anyone of: RDiscount, RedCarpet, BlueCloth, kramdown, maruku
File Extensions .markdown, .mkd and .md
Example markdown :index, :layout_engine => :erb

It is not possible to call methods from markdown, nor to pass locals to it. You therefore will usually use it in combination with another rendering engine:

ruby erb :overview, :locals => { :text => markdown(:introduction) }

Note that you may also call the markdown method from within other templates:

ruby %h1 Hello From Haml! %p= markdown(:greetings)

Since you cannot call Ruby from Markdown, you cannot use layouts written in Markdown. However, it is possible to use another rendering engine for the template than for the layout by passing the :layout_engine option.

Textile Templates

Dependency RedCloth
File Extension .textile
Example textile :index, :layout_engine => :erb

It is not possible to call methods from textile, nor to pass locals to it. You therefore will usually use it in combination with another rendering engine:

ruby erb :overview, :locals => { :text => textile(:introduction) }

Note that you may also call the textile method from within other templates:

ruby %h1 Hello From Haml! %p= textile(:greetings)

Since you cannot call Ruby from Textile, you cannot use layouts written in Textile. However, it is possible to use another rendering engine for the template than for the layout by passing the :layout_engine option.

RDoc Templates

Dependency RDoc
File Extension .rdoc
Example rdoc :README, :layout_engine => :erb

It is not possible to call methods from rdoc, nor to pass locals to it. You therefore will usually use it in combination with another rendering engine:

ruby erb :overview, :locals => { :text => rdoc(:introduction) }

Note that you may also call the rdoc method from within other templates:

ruby %h1 Hello From Haml! %p= rdoc(:greetings)

Since you cannot call Ruby from RDoc, you cannot use layouts written in RDoc. However, it is possible to use another rendering engine for the template than for the layout by passing the :layout_engine option.

AsciiDoc Templates

Dependency Asciidoctor
File Extension .asciidoc, .adoc and .ad
Example asciidoc :README, :layout_engine => :erb

Since you cannot call Ruby methods directly from an AsciiDoc template, you almost always want to pass locals to it.

Radius Templates

Dependency Radius
File Extension .radius
Example radius :index, :locals => { :key => 'value' }

Since you cannot call Ruby methods directly from a Radius template, you almost always want to pass locals to it.

Markaby Templates

Dependency Markaby
File Extension .mab
Example markaby { h1 "Welcome!" }

It also takes a block for inline templates (see example).

RABL Templates

Dependency Rabl
File Extension .rabl
Example rabl :index

Slim Templates

Dependency Slim Lang
File Extension .slim
Example slim :index

Creole Templates

Dependency Creole
File Extension .creole
Example creole :wiki, :layout_engine => :erb

It is not possible to call methods from creole, nor to pass locals to it. You therefore will usually use it in combination with another rendering engine:

ruby erb :overview, :locals => { :text => creole(:introduction) }

Note that you may also call the creole method from within other templates:

ruby %h1 Hello From Haml! %p= creole(:greetings)

Since you cannot call Ruby from Creole, you cannot use layouts written in Creole. However, it is possible to use another rendering engine for the template than for the layout by passing the :layout_engine option.

MediaWiki Templates

Dependency WikiCloth
File Extension .mediawiki and .mw
Example mediawiki :wiki, :layout_engine => :erb

It is not possible to call methods from MediaWiki markup, nor to pass locals to it. You therefore will usually use it in combination with another rendering engine:

ruby erb :overview, :locals => { :text => mediawiki(:introduction) }

Note that you may also call the mediawiki method from within other templates:

ruby %h1 Hello From Haml! %p= mediawiki(:greetings)

Since you cannot call Ruby from MediaWiki, you cannot use layouts written in MediaWiki. However, it is possible to use another rendering engine for the template than for the layout by passing the :layout_engine option.

CoffeeScript Templates

Dependency CoffeeScript and a way to execute javascript
File Extension .coffee
Example coffee :index

Stylus Templates

Dependency Stylus and a way to execute javascript
File Extension .styl
Example stylus :index

Before being able to use Stylus templates, you need to load stylus and stylus/tilt first:

``` ruby require ‘sinatra’ require ‘stylus’ require ‘stylus/tilt’

get ‘/’ do stylus :example end ```

Yajl Templates

Dependency yajl-ruby
File Extension .yajl
Example yajl :index, :locals => { :key => 'qux' }, :callback => 'present', :variable => 'resource'

The template source is evaluated as a Ruby string, and the resulting json variable is converted using #to_json:

ruby json = { :foo => 'bar' } json[:baz] = key

The :callback and :variable options can be used to decorate the rendered object:

javascript var resource = {"foo":"bar","baz":"qux"}; present(resource);

WLang Templates

Dependency WLang
File Extension .wlang
Example wlang :index, :locals => { :key => 'value' }

Since calling ruby methods is not idiomatic in WLang, you almost always want to pass locals to it. Layouts written in WLang and yield are supported, though.

Accessing Variables in Templates

Templates are evaluated within the same context as route handlers. Instance variables set in route handlers are directly accessible by templates:

ruby get '/:id' do @foo = Foo.find(params[:id]) haml '%h1=' end

Or, specify an explicit Hash of local variables:

ruby get '/:id' do foo = Foo.find(params[:id]) haml '%h1=', :locals => { :bar => foo } end

This is typically used when rendering templates as partials from within other templates.

Templates with yield and nested layouts

A layout is usually just a template that calls yield. Such a template can be used either through the :template option as described above, or it can be rendered with a block as follows:

ruby erb :post, :layout => false do erb :index end

This code is mostly equivalent to erb :index, :layout => :post.

Passing blocks to rendering methods is most useful for creating nested layouts:

ruby erb :main_layout, :layout => false do erb :admin_layout do erb :user end end

This can also be done in fewer lines of code with:

ruby erb :admin_layout, :layout => :main_layout do erb :user end

Currently, the following rendering methods accept a block: erb, haml, liquid, slim , wlang. Also the general render method accepts a block.

Inline Templates

Templates may be defined at the end of the source file:

``` ruby require ‘sinatra’

get ‘/’ do haml :index end


@@ layout %html = yield

@@ index %div.title Hello world. ```

NOTE: Inline templates defined in the source file that requires sinatra are automatically loaded. Call enable :inline_templates explicitly if you have inline templates in other source files.

Named Templates

Templates may also be defined using the top-level template method:

``` ruby template :layout do “%html\n =yield\n” end

template :index do ‘%div.title Hello World!’ end

get ‘/’ do haml :index end ```

If a template named “layout” exists, it will be used each time a template is rendered. You can individually disable layouts by passing :layout => false or disable them by default via set :haml, :layout => false:

ruby get '/' do haml :index, :layout => !request.xhr? end

Associating File Extensions

To associate a file extension with a template engine, use Tilt.register. For instance, if you like to use the file extension tt for Textile templates, you can do the following:

ruby Tilt.register :tt, Tilt[:textile]

Adding Your Own Template Engine

First, register your engine with Tilt, then create a rendering method:

``` ruby Tilt.register :myat, MyAwesomeTemplateEngine

helpers do def myat(*args) render(:myat, *args) end end

get ‘/’ do myat :index end ```

Renders ./views/index.myat. See to learn more about Tilt.


Before filters are evaluated before each request within the same context as the routes will be and can modify the request and response. Instance variables set in filters are accessible by routes and templates:

``` ruby before do @note = ‘Hi!’ request.path_info = ‘/foo/bar/baz’ end

get ‘/foo/*’ do @note #=> ‘Hi!’ params[:splat] #=> ‘bar/baz’ end ```

After filters are evaluated after each request within the same context as the routes will be and can also modify the request and response. Instance variables set in before filters and routes are accessible by after filters:

ruby after do puts response.status end

Note: Unless you use the body method rather than just returning a String from the routes, the body will not yet be available in the after filter, since it is generated later on.

Filters optionally take a pattern, causing them to be evaluated only if the request path matches that pattern:

``` ruby before ‘/protected/*’ do authenticate! end

after ‘/create/:slug’ do |slug| session[:last_slug] = slug end ```

Like routes, filters also take conditions:

``` ruby before :agent => /Songbird/ do # … end

after ‘/blog/*’, :host_name => ‘’ do # … end ```


Use the top-level helpers method to define helper methods for use in route handlers and templates:

``` ruby helpers do def bar(name) “#namebar” end end

get ‘/:name’ do bar(params[:name]) end ```

Alternatively, helper methods can be separately defined in a module:

``` ruby module FooUtils def foo(name) “#namefoo” end end

module BarUtils def bar(name) “#namebar” end end

helpers FooUtils, BarUtils ```

The effect is the same as including the modules in the application class.

Using Sessions

A session is used to keep state during requests. If activated, you have one session hash per user session:

``` ruby enable :sessions

get ‘/’ do “value = “ « session[:value].inspect end

get ‘/:value’ do session[:value] = params[:value] end ```

Note that enable :sessions actually stores all data in a cookie. This might not always be what you want (storing lots of data will increase your traffic, for instance). You can use any Rack session middleware: in order to do so, do not call enable :sessions, but instead pull in your middleware of choice as you would any other middleware:

``` ruby use Rack::Session::Pool, :expire_after => 2592000

get ‘/’ do “value = “ « session[:value].inspect end

get ‘/:value’ do session[:value] = params[:value] end ```

To improve security, the session data in the cookie is signed with a session secret. A random secret is generated for you by Sinatra. However, since this secret will change with every start of your application, you might want to set the secret yourself, so all your application instances share it:

ruby set :session_secret, 'super secret'

If you want to configure it further, you may also store a hash with options in the sessions setting:

ruby set :sessions, :domain => ''

To share your session across other apps on subdomains of, prefix the domain with a . like this instead:

ruby set :sessions, :domain => ''


To immediately stop a request within a filter or route use:

ruby halt

You can also specify the status when halting:

ruby halt 410

Or the body:

ruby halt 'this will be the body'

Or both:

ruby halt 401, 'go away!'

With headers:

ruby halt 402, {'Content-Type' => 'text/plain'}, 'revenge'

It is of course possible to combine a template with halt:

ruby halt erb(:error)


A route can punt processing to the next matching route using pass:

``` ruby get ‘/guess/:who’ do pass unless params[:who] == ‘Frank’ ‘You got me!’ end

get ‘/guess/*’ do ‘You missed!’ end ```

The route block is immediately exited and control continues with the next matching route. If no matching route is found, a 404 is returned.

Triggering Another Route

Sometimes pass is not what you want, instead you would like to get the result of calling another route. Simply use call to achieve this:

``` ruby get ‘/foo’ do status, headers, body = call env.merge(“PATH_INFO” => ‘/bar’) [status, headers,] end

get ‘/bar’ do “bar” end ```

Note that in the example above, you would ease testing and increase performance by simply moving "bar" into a helper used by both /foo and /bar.

If you want the request to be sent to the same application instance rather than a duplicate, use call! instead of call.

Check out the Rack specification if you want to learn more about call.

Setting Body, Status Code and Headers

It is possible and recommended to set the status code and response body with the return value of the route block. However, in some scenarios you might want to set the body at an arbitrary point in the execution flow. You can do so with the body helper method. If you do so, you can use that method from there on to access the body:

``` ruby get ‘/foo’ do body “bar” end

after do puts body end ```

It is also possible to pass a block to body, which will be executed by the Rack handler (this can be used to implement streaming, see “Return Values”).

Similar to the body, you can also set the status code and headers:

ruby get '/foo' do status 418 headers \ "Allow" => "BREW, POST, GET, PROPFIND, WHEN", "Refresh" => "Refresh: 20;" body "I'm a tea pot!" end

Like body, headers and status with no arguments can be used to access their current values.

Streaming Responses

Sometimes you want to start sending out data while still generating parts of the response body. In extreme examples, you want to keep sending data until the client closes the connection. You can use the stream helper to avoid creating your own wrapper:

ruby get '/' do stream do |out| out << "It's gonna be legen -\n" sleep 0.5 out << " (wait for it) \n" sleep 1 out << "- dary!\n" end end

This allows you to implement streaming APIs, Server Sent Events, and can be used as the basis for WebSockets. It can also be used to increase throughput if some but not all content depends on a slow resource.

Note that the streaming behavior, especially the number of concurrent requests, highly depends on the web server used to serve the application. Some servers, like WEBRick, might not even support streaming at all. If the server does not support streaming, the body will be sent all at once after the block passed to stream finishes executing. Streaming does not work at all with Shotgun.

If the optional parameter is set to keep_open, it will not call close on the stream object, allowing you to close it at any later point in the execution flow. This only works on evented servers, like Thin and Rainbows. Other servers will still close the stream:

``` ruby # long polling

set :server, :thin connections = []

get ‘/subscribe’ do # register a client’s interest in server events stream(:keep_open) { |out| connections « out }

# purge dead connections connections.reject!(&:closed?)

# acknowledge “subscribed” end

post ‘/message’ do connections.each do |out| # notify client that a new message has arrived out « params[:message] « “\n”

# indicate client to connect again
out.close   end

# acknowledge “message received” end ```


In the request scope, the logger helper exposes a Logger instance:

ruby get '/' do "loading data" # ... end

This logger will automatically take your Rack handler’s logging settings into account. If logging is disabled, this method will return a dummy object, so you do not have to worry about it in your routes and filters.

Note that logging is only enabled for Sinatra::Application by default, so if you inherit from Sinatra::Base, you probably want to enable it yourself:

ruby class MyApp < Sinatra::Base configure :production, :development do enable :logging end end

To avoid any logging middleware to be set up, set the logging setting to nil. However, keep in mind that logger will in that case return nil. A common use case is when you want to set your own logger. Sinatra will use whatever it will find in env['rack.logger'].

Mime Types

When using send_file or static files you may have mime types Sinatra doesn’t understand. Use mime_type to register them by file extension:

ruby configure do mime_type :foo, 'text/foo' end

You can also use it with the content_type helper:

ruby get '/' do content_type :foo "foo foo foo" end

Generating URLs

For generating URLs you should use the url helper method, for instance, in Haml:

ruby %a{:href => url('/foo')} foo

It takes reverse proxies and Rack routers into account, if present.

This method is also aliased to to (see below for an example).

Browser Redirect

You can trigger a browser redirect with the redirect helper method:

ruby get '/foo' do redirect to('/bar') end

Any additional parameters are handled like arguments passed to halt:

ruby redirect to('/bar'), 303 redirect '', 'wrong place, buddy'

You can also easily redirect back to the page the user came from with redirect back:

``` ruby get ‘/foo’ do “do something” end

get ‘/bar’ do do_something redirect back end ```

To pass arguments with a redirect, either add them to the query:

ruby redirect to('/bar?sum=42')

Or use a session:

``` ruby enable :sessions

get ‘/foo’ do session[:secret] = ‘foo’ redirect to(‘/bar’) end

get ‘/bar’ do session[:secret] end ```

Cache Control

Setting your headers correctly is the foundation for proper HTTP caching.

You can easily set the Cache-Control header like this:

ruby get '/' do cache_control :public "cache it!" end

Pro tip: Set up caching in a before filter:

ruby before do cache_control :public, :must_revalidate, :max_age => 60 end

If you are using the expires helper to set the corresponding header, Cache-Control will be set automatically for you:

ruby before do expires 500, :public, :must_revalidate end

To properly use caches, you should consider using etag or last_modified. It is recommended to call those helpers before doing any heavy lifting, as they will immediately flush a response if the client already has the current version in its cache:

ruby get '/article/:id' do @article = Article.find params[:id] last_modified @article.updated_at etag @article.sha1 erb :article end

It is also possible to use a weak ETag:

ruby etag @article.sha1, :weak

These helpers will not do any caching for you, but rather feed the necessary information to your cache. If you are looking for a quick reverse-proxy caching solution, try rack-cache:

``` ruby require “rack/cache” require “sinatra”

use Rack::Cache

get ‘/’ do cache_control :public, :max_age => 36000 sleep 5 “hello” end ```

Use the :static_cache_control setting (see below) to add Cache-Control header info to static files.

According to RFC 2616, your application should behave differently if the If-Match or If-None-Match header is set to *, depending on whether the resource requested is already in existence. Sinatra assumes resources for safe (like get) and idempotent (like put) requests are already in existence, whereas other resources (for instance post requests) are treated as new resources. You can change this behavior by passing in a :new_resource option:

ruby get '/create' do etag '', :new_resource => true Article.create erb :new_article end

If you still want to use a weak ETag, pass in a :kind option:

ruby etag '', :new_resource => true, :kind => :weak

Sending Files

For sending files, you can use the send_file helper method:

ruby get '/' do send_file 'foo.png' end

It also takes options:

ruby send_file 'foo.png', :type => :jpg

The options are:

file name, in response, defaults to the real file name.
value for Last-Modified header, defaults to the file's mtime.
content type to use, guessed from the file extension if missing.
used for Content-Disposition, possible value: nil (default), :attachment and :inline
Content-Length header, defaults to file size.
Status code to be sent. Useful when sending a static file as an error page. If supported by the Rack handler, other means than streaming from the Ruby process will be used. If you use this helper method, Sinatra will automatically handle range requests.

Accessing the Request Object

The incoming request object can be accessed from request level (filter, routes, error handlers) through the request method:

ruby # app running on get '/foo' do t = %w[text/css text/html application/javascript] request.accept # ['text/html', '*/*'] request.accept? 'text/xml' # true request.preferred_type(t) # 'text/html' request.body # request body sent by the client (see below) request.scheme # "http" request.script_name # "/example" request.path_info # "/foo" request.port # 80 request.request_method # "GET" request.query_string # "" request.content_length # length of request.body request.media_type # media type of request.body # "" request.get? # true (similar methods for other verbs) request.form_data? # false request["some_param"] # value of some_param parameter. [] is a shortcut to the params hash. request.referrer # the referrer of the client or '/' request.user_agent # user agent (used by :agent condition) request.cookies # hash of browser cookies request.xhr? # is this an ajax request? request.url # "" request.path # "/example/foo" request.ip # client IP address # false (would be true over ssl) request.forwarded? # true (if running behind a reverse proxy) request.env # raw env hash handed in by Rack end

Some options, like script_name or path_info, can also be written:

``` ruby before { request.path_info = “/” }

get “/” do “all requests end up here” end ```

The request.body is an IO or StringIO object:

ruby post "/api" do request.body.rewind # in case someone already read it data = JSON.parse "Hello #{data['name']}!" end


You can use the attachment helper to tell the browser the response should be stored on disk rather than displayed in the browser:

ruby get '/' do attachment "store it!" end

You can also pass it a file name:

ruby get '/' do attachment "info.txt" "store it!" end

Dealing with Date and Time

Sinatra offers a time_for helper method that generates a Time object from the given value. It is also able to convert DateTime, Date and similar classes:

ruby get '/' do pass if > time_for('Dec 23, 2012') "still time" end

This method is used internally by expires, last_modified and akin. You can therefore easily extend the behavior of those methods by overriding time_for in your application:

``` ruby helpers do def time_for(value) case value when :yesterday then - 246060 when :tomorrow then + 246060 else super end end end

get ‘/’ do last_modified :yesterday expires :tomorrow “hello” end ```

Looking Up Template Files

The find_template helper is used to find template files for rendering:

ruby find_template settings.views, 'foo', Tilt[:haml] do |file| puts "could be #{file}" end

This is not really useful. But it is useful that you can actually override this method to hook in your own lookup mechanism. For instance, if you want to be able to use more than one view directory:

``` ruby set :views, [‘views’, ‘templates’]

helpers do def find_template(views, name, engine, &block) Array(views).each { |v| super(v, name, engine, &block) } end end ```

Another example would be using different directories for different engines:

``` ruby set :views, :sass => ‘views/sass’, :haml => ‘templates’, :default => ‘views’

helpers do def find_template(views, name, engine, &block) _, folder = views.detect { |k,v| engine == Tilt[k] } folder ||= views[:default] super(folder, name, engine, &block) end end ```

You can also easily wrap this up in an extension and share with others!

Note that find_template does not check if the file really exists but rather calls the given block for all possible paths. This is not a performance issue, since render will use break as soon as a file is found. Also, template locations (and content) will be cached if you are not running in development mode. You should keep that in mind if you write a really crazy method.


Run once, at startup, in any environment:

``` ruby configure do # setting one option set :option, ‘value’

# setting multiple options set :a => 1, :b => 2

# same as set :option, true enable :option

# same as set :option, false disable :option

# you can also have dynamic settings with blocks set(:css_dir) { File.join(views, ‘css’) } end ```

Run only when the environment (RACK_ENV environment variable) is set to :production:

ruby configure :production do ... end

Run when the environment is set to either :production or :test:

ruby configure :production, :test do ... end

You can access those options via settings:

``` ruby configure do set :foo, ‘bar’ end

get ‘/’ do # => true # => ‘bar’ … end ```

Configuring attack protection

Sinatra is using Rack::Protection to defend your application against common, opportunistic attacks. You can easily disable this behavior (which will open up your application to tons of common vulnerabilities):

ruby disable :protection

To skip a single defense layer, set protection to an options hash:

ruby set :protection, :except => :path_traversal You can also hand in an array in order to disable a list of protections:

ruby set :protection, :except => [:path_traversal, :session_hijacking]

By default, Sinatra will only set up session based protection if :sessions has been enabled. Sometimes you want to set up sessions on your own, though. In that case you can get it to set up session based protections by passing the :session option:

ruby use Rack::Session::Pool set :protection, :session => true

Available Settings

If disabled, Sinatra will allow relative redirects, however, Sinatra will no longer conform with RFC 2616 (HTTP 1.1), which only allows absolute redirects.
Enable if your app is running behind a reverse proxy that has not been set up properly. Note that the url helper will still produce absolute URLs, unless you pass in false as the second parameter.
Disabled by default.
Mime types the content_type helper will automatically add the charset info to. You should add to it rather than overriding this option: settings.add_charsets << "application/foobar"
Path to the main application file, used to detect project root, views and public folder and inline templates.
IP address to bind to (default: or localhost if your `environment` is set to development.). Only used for built-in server.
Encoding to assume if unknown (defaults to "utf-8").
Display errors in the log.
Current environment. Defaults to ENV['RACK_ENV'], or "development" if not available.
Use the logger.
Places a lock around every request, only running processing on request per Ruby process concurrently.
Enabled if your app is not thread-safe. Disabled per default.
Use _method magic to allow put/delete forms in browsers that don't support it.
Port to listen on. Only used for built-in server.
Whether or not to insert request.script_name into redirects if no absolute path is given. That way redirect '/foo' would behave like redirect to('/foo'). Disabled per default.
Whether or not to enable web attack protections. See protection section above.
Alias for public_folder. See below.
Path to the folder public files are served from. Only used if static file serving is enabled (see static setting below). Inferred from app_file setting if not set.
Whether or not to reload templates between requests. Enabled in development mode.
Path to project root folder. Inferred from app_file setting if not set.
Raise exceptions (will stop application). Enabled by default when environment is set to "test", disabled otherwise.
If enabled, Sinatra will handle starting the web server. Do not enable if using rackup or other means.
Is the built-in server running now? Do not change this setting!
Server or list of servers to use for built-in server. Order indicates priority, default depends on Ruby implementation.
Enable cookie-based sessions support using Rack::Session::Cookie. See 'Using Sessions' section for more information.
Show a stack trace in the browser when an exception happens. Enabled by default when environment is set to "development", disabled otherwise.
Can also be set to :after_handler to trigger app-specified error handling before showing a stack trace in the browser.
Whether Sinatra should handle serving static files.
Disable when using a server able to do this on its own.
Disabling will boost performance.
Enabled per default in classic style, disabled for modular apps.
When Sinatra is serving static files, set this to add Cache-Control headers to the responses. Uses the cache_control helper. Disabled by default.
Use an explicit array when setting multiple values: set :static_cache_control, [:public, :max_age => 300]
If set to true, will tell Thin to use EventMachine.defer for processing the request.
Whether Sinatra should handle system signals.
Path to the views folder. Inferred from app_file setting if not set.
Whether or not to set the X-Cascade header if no route matches. Defaults to true.


There are three predefined environments: "development", "production" and "test". Environments can be set through the RACK_ENV environment variable. The default value is "development". In the "development" environment all templates are reloaded between requests, and special not_found and error handlers display stack traces in your browser. In the "production" and "test" environments, templates are cached by default.

To run different environments, set the RACK_ENV environment variable:

shell RACK_ENV=production ruby my_app.rb

You can use predefined methods: development?, test? and production? to check the current environment setting:

ruby get '/' do if settings.development? "development!" else "not development!" end end

Error Handling

Error handlers run within the same context as routes and before filters, which means you get all the goodies it has to offer, like haml, erb, halt, etc.

Not Found

When a Sinatra::NotFound exception is raised, or the response’s status code is 404, the not_found handler is invoked:

ruby not_found do 'This is nowhere to be found.' end


The error handler is invoked any time an exception is raised from a route block or a filter. The exception object can be obtained from the sinatra.error Rack variable:

ruby error do 'Sorry there was a nasty error - ' + env['sinatra.error'].name end

Custom errors:

ruby error MyCustomError do 'So what happened was...' + env['sinatra.error'].message end

Then, if this happens:

ruby get '/' do raise MyCustomError, 'something bad' end

You get this:

So what happened was... something bad

Alternatively, you can install an error handler for a status code:

``` ruby error 403 do ‘Access forbidden’ end

get ‘/secret’ do 403 end ```

Or a range:

ruby error 400..510 do 'Boom' end

Sinatra installs special not_found and error handlers when running under the development environment to display nice stack traces and additional debugging information in your browser.

Rack Middleware

Sinatra rides on Rack, a minimal standard interface for Ruby web frameworks. One of Rack’s most interesting capabilities for application developers is support for “middleware” – components that sit between the server and your application monitoring and/or manipulating the HTTP request/response to provide various types of common functionality.

Sinatra makes building Rack middleware pipelines a cinch via a top-level use method:

``` ruby require ‘sinatra’ require ‘my_custom_middleware’

use Rack::Lint use MyCustomMiddleware

get ‘/hello’ do ‘Hello World’ end ```

The semantics of use are identical to those defined for the Rack::Builder DSL (most frequently used from rackup files). For example, the use method accepts multiple/variable args as well as blocks:

ruby use Rack::Auth::Basic do |username, password| username == 'admin' && password == 'secret' end

Rack is distributed with a variety of standard middleware for logging, debugging, URL routing, authentication, and session handling. Sinatra uses many of these components automatically based on configuration so you typically don’t have to use them explicitly.

You can find useful middleware in rack, rack-contrib, or in the Rack wiki.


Sinatra tests can be written using any Rack-based testing library or framework. Rack::Test is recommended:

``` ruby require ‘my_sinatra_app’ require ‘test/unit’ require ‘rack/test’

class MyAppTest < Test::Unit::TestCase include Rack::Test::Methods

def app Sinatra::Application end

def test_my_default get ‘/’ assert_equal ‘Hello World!’, last_response.body end

def test_with_params get ‘/meet’, :name => ‘Frank’ assert_equal ‘Hello Frank!’, last_response.body end

def test_with_rack_env get ‘/’, {}, ‘HTTP_USER_AGENT’ => ‘Songbird’ assert_equal “You’re using Songbird!”, last_response.body end end ```

Note: If you are using Sinatra in the modular style, replace Sinatra::Application above with the class name of your app.

Sinatra::Base - Middleware, Libraries, and Modular Apps

Defining your app at the top-level works well for micro-apps but has considerable drawbacks when building reusable components such as Rack middleware, Rails metal, simple libraries with a server component, or even Sinatra extensions. The top-level assumes a micro-app style configuration (e.g., a single application file, ./public and ./views directories, logging, exception detail page, etc.). That’s where Sinatra::Base comes into play:

``` ruby require ‘sinatra/base’

class MyApp < Sinatra::Base set :sessions, true set :foo, ‘bar’

get ‘/’ do ‘Hello world!’ end end ```

The methods available to Sinatra::Base subclasses are exactly the same as those available via the top-level DSL. Most top-level apps can be converted to Sinatra::Base components with two modifications:

Sinatra::Base is a blank slate. Most options are disabled by default, including the built-in server. See Configuring Settings for details on available options and their behavior. If you want behavior more similar to when you define your app at the top level (also know as Classic style), you can subclass Sinatra::Application.

``` ruby require ‘sinatra/base’

class MyApp < Sinatra::Application get ‘/’ do ‘Hello world!’ end end ```

Modular vs. Classic Style

Contrary to common belief, there is nothing wrong with the classic style. If it suits your application, you do not have to switch to a modular application.

The main disadvantage of using the classic style rather than the modular style is that you will only have one Sinatra application per Ruby process. If you plan to use more than one, switch to the modular style. There is no reason you cannot mix the modular and the classic styles.

If switching from one style to the other, you should be aware of slightly different default settings:

Setting Classic Modular Modular
app_file file loading sinatra file subclassing Sinatra::Base file subclassing Sinatra::Application
run $0 == app_file false false
logging true false true
method_override true false true
inline_templates true false true
static true false true

Serving a Modular Application

There are two common options for starting a modular app, actively starting with run!:

``` ruby # my_app.rb require ‘sinatra/base’

class MyApp < Sinatra::Base # … app code here …

# start the server if ruby file executed directly run! if app_file == $0 end ```

Start with:

shell ruby my_app.rb

Or with a file, which allows using any Rack handler:

ruby # (run with rackup) require './my_app' run MyApp


shell rackup -p 4567

Using a Classic Style Application with a

Write your app file:

``` ruby # app.rb require ‘sinatra’

get ‘/’ do ‘Hello world!’ end ```

And a corresponding

ruby require './app' run Sinatra::Application

When to use a

A file is recommended if:

There is no need to switch to a simply because you switched to the modular style, and you don’t have to use the modular style for running with a

Using Sinatra as Middleware

Not only is Sinatra able to use other Rack middleware, any Sinatra application can in turn be added in front of any Rack endpoint as middleware itself. This endpoint could be another Sinatra application, or any other Rack-based application (Rails/Ramaze/Camping/…):

``` ruby require ‘sinatra/base’

class LoginScreen < Sinatra::Base enable :sessions

get(‘/login’) { haml :login }

post(‘/login’) do if params[:name] == ‘admin’ && params[:password] == ‘admin’ session[‘user_name’] = params[:name] else redirect ‘/login’ end end end

class MyApp < Sinatra::Base # middleware will run before filters use LoginScreen

before do unless session[‘user_name’] halt “Access denied, please login.” end end

get(‘/’) { “Hello #session[‘user_name’].” } end ```

Dynamic Application Creation

Sometimes you want to create new applications at runtime without having to assign them to a constant. You can do this with

ruby require 'sinatra/base' my_app = { get('/') { "hi" } }!

It takes the application to inherit from as an optional argument:

```ruby # (run with rackup) require ‘sinatra/base’

controller = do enable :logging helpers MyHelpers end

map(‘/a’) do run { get(‘/’) { ‘a’ } } end

map(‘/b’) do run { get(‘/’) { ‘b’ } } end ```

This is especially useful for testing Sinatra extensions or using Sinatra in your own library.

This also makes using Sinatra as middleware extremely easy:

``` ruby require ‘sinatra/base’

use Sinatra do get(‘/’) { … } end

run RailsProject::Application ```

Scopes and Binding

The scope you are currently in determines what methods and variables are available.

Application/Class Scope

Every Sinatra application corresponds to a subclass of Sinatra::Base. If you are using the top-level DSL (require 'sinatra'), then this class is Sinatra::Application, otherwise it is the subclass you created explicitly. At class level you have methods like get or before, but you cannot access the request or session objects, as there is only a single application class for all requests.

Options created via set are methods at class level:

``` ruby class MyApp < Sinatra::Base # Hey, I’m in the application scope! set :foo, 42 foo # => 42

get ‘/foo’ do # Hey, I’m no longer in the application scope! end end ```

You have the application scope binding inside:

You can reach the scope object (the class) like this:

Request/Instance Scope

For every incoming request, a new instance of your application class is created, and all handler blocks run in that scope. From within this scope you can access the request and session objects or call rendering methods like erb or haml. You can access the application scope from within the request scope via the settings helper:

``` ruby class MyApp < Sinatra::Base # Hey, I’m in the application scope! get ‘/define_route/:name’ do # Request scope for ‘/define_route/:name’ @value = 42

settings.get("/#{params[:name]}") do
  # Request scope for "/#{params[:name]}"
  @value # => nil (not the same request)

"Route defined!"   end end ```

You have the request scope binding inside:

Delegation Scope

The delegation scope just forwards methods to the class scope. However, it does not behave exactly like the class scope, as you do not have the class binding. Only methods explicitly marked for delegation are available, and you do not share variables/state with the class scope (read: you have a different self). You can explicitly add method delegations by calling Sinatra::Delegator.delegate :method_name.

You have the delegate scope binding inside:

Have a look at the code for yourself: here’s the Sinatra::Delegator mixin being extending the main object.

Command Line

Sinatra applications can be run directly:

shell ruby myapp.rb [-h] [-x] [-e ENVIRONMENT] [-p PORT] [-o HOST] [-s HANDLER]

Options are:

-h # help -p # set the port (default is 4567) -o # set the host (default is -e # set the environment (default is development) -s # specify rack server/handler (default is thin) -x # turn on the mutex lock (default is off)


The following Ruby versions are officially supported:

Ruby 1.8.7
1.8.7 is fully supported, however, if nothing is keeping you from it, we recommend upgrading or switching to JRuby or Rubinius. Support for 1.8.7 will not be dropped before Sinatra 2.0. Ruby 1.8.6 is no longer supported.
Ruby 1.9.2
1.9.2 is fully supported. Do not use 1.9.2p0, as it is known to cause segmentation faults when running Sinatra. Official support will continue at least until the release of Sinatra 1.5.
Ruby 1.9.3
1.9.3 is fully supported and recommended. Please note that switching to 1.9.3 from an earlier version will invalidate all sessions. 1.9.3 will be supported until the release of Sinatra 2.0.
Ruby 2.0.0
2.0.0 is fully supported and recommended. There are currently no plans to drop official support for it.
Rubinius is officially supported (Rubinius >= 2.x). It is recommended to gem install puma.
The latest stable release of JRuby is officially supported. It is not recommended to use C extensions with JRuby. It is recommended to gem install trinidad.

We also keep an eye on upcoming Ruby versions.

The following Ruby implementations are not officially supported but still are known to run Sinatra:

Not being officially supported means if things only break there and not on a supported platform, we assume it’s not our issue but theirs.

We also run our CI against ruby-head (the upcoming 2.1.0), but we can’t guarantee anything, since it is constantly moving. Expect 2.1.0 to be fully supported.

Sinatra should work on any operating system supported by the chosen Ruby implementation.

If you run MacRuby, you should gem install control_tower.

Sinatra currently doesn’t run on Cardinal, SmallRuby, BlueRuby or any Ruby version prior to 1.8.7.

The Bleeding Edge

If you would like to use Sinatra’s latest bleeding-edge code, feel free to run your application against the master branch, it should be rather stable.

We also push out prerelease gems from time to time, so you can do a

shell gem install sinatra --pre

to get some of the latest features.

With Bundler

If you want to run your application with the latest Sinatra, using Bundler is the recommended way.

First, install bundler, if you haven’t:

shell gem install bundler

Then, in your project directory, create a Gemfile:

```ruby source ‘’ gem ‘sinatra’, :github => “sinatra/sinatra”

other dependencies

gem ‘haml’ # for instance, if you use haml gem ‘activerecord’, ‘~> 3.0’ # maybe you also need ActiveRecord 3.x ```

Note that you will have to list all your application’s dependencies in the Gemfile. Sinatra’s direct dependencies (Rack and Tilt) will, however, be automatically fetched and added by Bundler.

Now you can run your app like this:

shell bundle exec ruby myapp.rb

Roll Your Own

Create a local clone and run your app with the sinatra/lib directory on the $LOAD_PATH:

shell cd myapp git clone git:// ruby -I sinatra/lib myapp.rb

To update the Sinatra sources in the future:

shell cd myapp/sinatra git pull

Install Globally

You can build the gem on your own:

shell git clone git:// cd sinatra rake sinatra.gemspec rake install

If you install gems as root, the last step should be:

shell sudo rake install


Sinatra follows Semantic Versioning, both SemVer and SemVerTag.

Further Reading